1. Field of the Invention
This invention relates to a method for monitoring the condition of steel-reinforced concrete structures, and more specifically to a method of determining the onset of corrosion at the interface of a steel reinforcing member and the concrete of a structure reinforced by the member.
One of the persistent unsolved problems encountered in use of steel-reinforced concrete for highway bridge decks is that ice-clearing brine solutions penetrate the concrete and corrode the steel reinforcing members, resulting in destruction of the bond between the reinforcing member and the concrete. Destruction of this bond weakens the bridge deck and eventually necessitates repair or replacement.
The present invention does not eliminate the problem, but provides a means for detecting and studying the problem, and also provides an advance indication of a potential safety hazard.
2. Description of the Prior Art
Heretofore there has been no effective way of detecting the onset of corrosion at the reinforcing steel-concrete interface in the interior of a concrete structure. Thus, it was only after visible damage to the concrete structure was detected that a problem was evident. In some cases an unsafe condition develops prior to visible evidence of deterioration.
In U.S. Pat. No. 3,942,546, an electronic hydrogen sensor is described which detects corrosion at the exterior surface of a hollow hydrogen-permeable probe member. The probe is connected to a getter-ion pump and evacuated to a high vacuum. A power supply is connected to the getter-ion pump, and the current output of the getter-ion pump is a function of the amount of hydrogen permeating the probe wall. A corrosive reaction occurring at the outer surface of the probe results in formation of atomic hydrogen, which permeates the hydrogen-permeable probe wall and produces an increased current output.
The present invention utilizes the hydrogen probe as described in detail in U.S. Pat. No. 3,942,546 to provide information regarding corrosion at the interface between steel reinforcing members and concrete in a reinforced concrete structure.